In the previous granting period, we developed techniques to use synthetic oligodeoxyribonucleotides as probes for the isolation of cloned DNAs coding for proteins of or related to the MHC. We have isolated a cDNA clone for human Beta2m and several cDNA clones for H2 class I antigens, including one clone coding for an H-2Kb related molecule. In this grant we propose to extend our efforts to the isolation of cloned DNAs (both cDNA and genomic DNA) of class I and class II antigens. The specific objectives are: 1. Isolate and completely sequence cDNA clones for several class I antigens to gain insight into the distribution of the polymorphic sites in the polypeptide chain. This is much more easily done by DNA sequencing than by protein sequencing (see Progress Report). 2. To isolate cDNA clones for murine Ia antigens using, as probes, clones isolated for human DR and IA antigens in collaboration with Drs. K. Itakura, J. Shively, and J. Silver. 3. To isolate genomic clones for class I and II antigens for which cDNA clones have already been obtained. 4. To isolate and sequence genomic nes for H2-Kb and various mutant alleles to help in understanding the very high mutation frequency in H2 genes. 5. To establish an in vivo assay in which phenotypic effects of in vitro generated mutations of cloned H2 genes can be assessed.